Thanks for taking the time to write. I’m curious - are all those prices from the same day? I’m looking at IllinoisGasPrices.com, another site I use, and they show Freeport prices at $3.25 to $3.33, while Rockford tends to run $3.25 to $3.36 (with one outlier on each end of the spectrum). Chicago, in comparison, starts in the $3.30s and heads up to the $3.60s. With prices fluctuated as they do, there will be times where the Chicago suburbs will dip or rise ahead of the Rockford area, and you can always find individual stations that will have prices out of sync at a given moment. But generally, the Rockford area is cheaper than Chicago, though not always cheaper than parts of the western suburbs.

As for the Wisconsin prices - Wisconsin as at least a 6.5 cent on average lower tax rate than Illinois. But Illinois’ gas tax is a rare percentage rate as opposed to the flat tax in Wisconsin … the higher prices go, the higher the tax is, increasing the disparity. Also, Illinois allows local taxes on gas, while Wisconsin doesn’t.

A similar dynamic is in Detroit - We have a 3.5 cent difference in tax rates, plus the above notes. And Michigan has been lower than Illinois in general for the past year, not just Rockford.

Let me know if you have further questions.